糖摄入可增加青少年脑血流量

旧金山——美国糖尿病协会年会上公布的一项研究显示，发育中的青少年大脑对含糖饮料的反应不同于成人，导致糖摄入量增加和加剧儿童肥胖流行现象。功能MRI扫描显示，在摄入葡萄糖后，青少年大脑的奖励和执行功能区域的血流量增加。

这项小样本量初步研究由耶鲁大学的Ania M. Jastreboff医生及其同事进行，入选14例体瘦青少年和20例体瘦成人，旨在比较这两组受试者在摄入75 g葡萄糖后的脑血流量。

这些受试者的平均体重指数为22 kg/m²，青少年和成人的平均年龄分别为16岁和31岁。

受试者在隔夜禁食后于早上8点来到研究中心。受试者进行基线MRI扫描、饮用75 g葡萄糖和进行功能MRI扫描。在1 h的扫描操作期间，每10 min测定1次实验室值。

结果显示，在体瘦青少年中，葡萄糖摄入导致纹状体、脑岛、前扣带回皮层和前额叶皮层血流增加，所有这些脑区均位于皮质纹状体边缘环路，在青少年期间发生显著发育改变。未观察到下丘脑和丘脑血流发生改变。

相比之下，体瘦成人摄入含糖饮料后，下丘脑、丘脑、纹状体、脑岛和前扣带皮层血流减少。未观察到前额叶皮层血流发生改变。

研究者推测，两组受试者在大脑对糖摄入反应方面的明显差异可能导致青少年增加含糖饮料的摄入。

研究结果非常不具有确定性

匹兹堡大学儿科教授Silva Arslanian医生表示，其对任何研究结果的重现性持怀疑态度，包括上述研究。尚不清楚该研究在两组受试者中观察到的差异是固有的差异还是环境驱动的差异。不过，有必要对这一最新研究数据进行进一步研究，以确定糖摄入最终会产生什么影响。

Jastreboff医生和Arslanian医生均声明无相关经济利益冲突。

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By: NASEEM S. MILLER, Internal Medicine News Digital Network

SAN FRANCISCO – The developing adolescent brain may be responding differently to sugary drinks, leading to higher consumption of sugars and feeding the childhood obesity epidemic, according to researchers.

The findings come from a small, preliminary study that compared cerebral blood flow in 14 lean adolescents and 20 lean adults brains after the study subjects ingested 75 g of glucose.

Functional MRI scans revealed that glucose ingestion increased cerebral blood flow in the reward and executive function areas of the teens’ brains.

"This study is the first step in understanding what is occurring in the developing adolescent brain in response to drinking sugar," said Dr. Ania M. Jastreboff of Yale University, New Haven, Conn.

Several areas of the brain regulate food intake. They include the hypothalamus; the striatal region, which includes the putamen and caudate and is in charge of motivation and reward; the limbic region, where emotion and memory reside; and the cortical region, which includes the prefrontal cortex, insula, and the anterior cingulate cortex and handles the integration and processing of the brain.

In a previous study, Dr. Jastreboff and colleagues showed that "obese, but not lean, individuals exhibited increased activation in striatal, insular, and hypothalamic regions during exposure to favorite-food" (Diabetes Care 2013;36:394-402).

The group also has shown that glucose ingestion in lean adults reduced cerebral blood flow in appetite-regulation and reward-processing regions of the brain, Dr. Jastreboff said at the annual scientific sessions of the American Diabetes Association.

Subsequently, they wanted to find out if lean adolescent brains, compared with brains of lean adults, responded differently to glucose.

Among the subjects, the average body mass index was 22 kg/m², and the mean age was 16 years for adolescents and 31 years for adults.

They came in at 8 a.m. after overnight fasting. They had a baseline MRI, drank 75 g of glucose, and had a functional MRI scan. Their labs were drawn every 10 minutes throughout the 1-hour scanning procedures.

Results showed that in lean adolescents, glucose ingestion increased cerebral blood flow in the striatum, insula, anterior cingulate cortex and the prefrontal cortex, all of which are regions of the brain that reside in the corticostriatal-limbic circuitry undergoing significant developmental changes during adolescence, said Dr. Jastreboff. There were no changes in hypothalamus and thalamus blood flow.

In contrast, consumption of the sugary drink in lean adults decreased cerebral blood flow in the hypothalamus, thalamus, striatum, insula, and the anterior cingulate cortex. There was no change in the prefrontal cortex.

"We hypothesize that these striking differences in brain response to glucose ingestion might contribute to adolescents’ higher consumption of added sugars," said Dr. Jastreboff.

She said that her group also conducted the study in obese adolescents and the results should be published soon. "What I can say is that the responses were different," she said.

The findings are far from definitive.

"I’m always skeptical that any test, if repeated the next day, will show the same thing," said Dr. Silva Arslanian, professor of pediatrics at the University of Pittsburgh. "The question is, is it an innate difference, or is it an environmental-driven difference?"

"But it’s definitely new data that needs to be pursued further to see what its translation is," said Dr. Arslanian, who was not involved in the study.

Dr. Jastreboff and Dr. Arslanian had no relevant disclosures.